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Intrinsic parameters (magnetic core composition, size, shape, coating, and surface functionalization) and extrinsic parameters (solvent, magnetic field, and temperature) relevant for describing the nuclear relaxation in MNP core–shell nanoparticles are discussed.

Phantoms mimicking human tissue heterogeneity and intensity are required to establish radiomic features robustness in Computed Tomography (CT) images. We developed inserts with two different techniques for the radiomic study of Non-Small Cell Lung Cancer (NSCLC) lesions.We developed two insert prototypes: two 3D-printed made of glycol-modified polyethylene terephthalate (PET-G), and nine with sodium polyacrylate plus iodinated contrast medium. The inserts were put in a handcraft phantom (HeLLePhant). We also analysed four materials of a commercial homogeneous phantom (Catphan® 424) and collected 29 NSCLC patients for comparison. All the CT acquisitions were performed with the same clinical protocol and scanner at 120kVp. The HeLLePhant phantom was scanned ten times in fixed condition at 120kVp and 100kVp for repeatability investigation. We extracted 153 radiomic features using Pyradiomics. To compare the features between phantoms and patients, we computed how many phantom features fell in the range between 10th and 90th percentile of the corresponding patient values. We deemed repeatable the features with a coefficient of variation (CV) less than or equal to 0.10.The best similarity with the patients was obtained with the polyacrylate inserts (55.6-90.2%), the worst with Catphan (15.7-19.0%). For the PET-G inserts 35.3% and 36.6% of the features match the patient range. We found high repeatability for all the inserts of the HeLLePhant phantom (74.3-100% at 120kVp, 75.7-97.9% at 100kVp), and observed a texture dependency in repeatability.Our study shows a promising way to construct heterogeneous inserts mimicking a target tissue for radiomic studies.

We present a proof-of-concept study focusing on a method for the intra- and inter-center validation and harmonization of data obtained from MRI T

Background and purpose In the retrospective-prospective multi-center "Blue Sky Radiomics” study (NCT04364776), we plan to test a pre-defined radiomic signature in a series of stage III unresectable NSCLC patients undergoing chemoradiotherapy and maintenance immunotherapy. As a necessary preliminary step, we explore the influence of different image-acquisition parameters on radiomic features’ reproducibility and apply methods for harmonization. Material and methods We identified the primary lung tumor on two computed tomography (CT) series for each patient, acquired before and after chemoradiation with i.v. contrast medium and with different scanners. Tumor segmentation was performed by two oncological imaging specialists (thoracic radiologist and radio-oncologist) using the Oncentra Masterplan® software. We extracted 42 radiomic features from the specific ROIs (LIFEx). To assess the impact of different acquisition parameters on features extraction, we used the Combat tool with nonparametric adjustment and the longitudinal version (LongComBat). Results We defined 14 CT acquisition protocols for the harmonization process. Before harmonization, 76% of the features were significantly influenced by these protocols. After, all extracted features resulted in being independent of the acquisition parameters. In contrast, 5% of the LongComBat harmonized features still depended on acquisition protocols. Conclusions We reduced the impact of different CT acquisition protocols on radiomic features extraction in a group of patients enrolled in a radiomic study on stage III NSCLC. The harmonization process appears essential for the quality of radiomic data and for their reproducibility. ClinicalTrials.gov Identifier: NCT04364776, First Posted:April 28, 2020, Actual Study Start Date: April 15, 2020, https://clinicaltrials.gov/ct2/show/NCT04364776.

By means of muon spin relaxation measurements we unraveled the temperature spin dynamics in monodisperse maghemite spherical nanoparticles with different surface to volume ratio, in two samples wit ...

We present a proof-of-concept study focusing on a method for the intra- and inter-center validation and harmonization of data obtained from MRI T1 and T2 maps. The method is based on a set of MnCl2 samples that provide in-scan ground-truth reference values regardless of the details of the MRI protocol. The relaxation times of MnCl2 aqueous solutions were first measured by means of an NMR laboratory relaxometer, as a function of concentration and temperature. The obtained T1 and T2 values, once renormalized at the scanner temperature, were used as reference values for the MRI mapping measurements of the MnCl2 relaxation times. By using different clinical MRI scanners and sequences, we found a good agreement for standard and turbo sequences (limits of agreement: 5% for IR, SE, IR-TSE; 10% for TSE), while an under-estimation and an over-estimation were found respectively for MOLLI and T2-prep TrueFISP, as already reported in the literature. The linearity of the relaxation rates with the concentration predicted by the Solomon-Bloembergen-Morgan theory was observed for every dataset at all temperatures, except for T2-prep TrueFISP maps results. Some preliminary results of an in vivo experiment are also presented.

Longitudinal and transverse 1H nuclear magnetic resonance relaxivities of Ln(III)-DOTA complexes (with Ln = Gd, Tb, Dy, Er; DOTA = 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid) and Mn(II) aqueous solutions were measured in a wide range of frequencies, 10 kHz to 700 MHz. The experimental data were interpreted by means of models derived from the Solomon–Bloembergen–Morgan theory. The data analysis was performed assuming the orbital angular momentum L = 0 for Gd-DOTA and the aqua ion [Mn(H2O)6]2+ and L ≠ 0 for Dy-, Tb-, and Er-DOTA. A refined estimation of the zero-field-splitting barrier Δ and of the modulation correlation time τv was obtained for [Mn(H2O)6]2+ by extending the fitting of nuclear magnetic relaxation dispersion profiles to the low-field regime. The Gd-DOTA fitting parameters resulted in good agreement with the literature, and the fit of transverse relaxivity data confirmed the negligibility of the scalar interaction in the nuclear relaxation mechanism. Larger transverse relaxivities of Dy-DOTA and Tb-DOTA (∼10 mM−1 s−1) with respect to Er-DOTA (∼1 mM−1 s−1) were observed at 16 T. Such higher values are suggested to be due to a shorter residence time τm that is possibly linked to the fluctuations of the hyperfine interaction and the different shape of the magnetic anisotropy. The possible employment of Dy-DOTA, Tb-DOTA, and Er-DOTA as negative magnetic resonance imaging contrast agents for high-field applications was envisaged by collecting spin-echo images at 7 T. Particularly in Dy- and Tb-derivatives, the transverse relaxivity at 16 T is of the order of the Gd-one at 1.5 T.

We present a 1H NMR investigation of spin dynamics in two finite integer spin molecular nanomagnetic rings, namely V7Zn and V7Ni. This study could be put in correlation with the problem of Haldane gap in infinite integer spin chains. While V7Zn is an approximation of a homometallic broken chain due to the presence of s = 0 Zn2+ ion uncoupled from nearest neighbor V2+s = 1 ions, the V7Ni compound constitutes an example of a closed periodical s = 1 heterometallic chain. From preliminary susceptibility measurements on single crystals and data analysis, the exchange coupling constant J/kB results in the order of few kelvin. At room temperature, the frequency behavior of the 1H NMR spin–lattice relaxation rate 1/T1 allowed to conclude that the spin–spin correlation function is similar to the one observed in semi-integer spin molecules, but with a smaller cutoff frequency. Thus, the high-T data can be interpreted in terms of, e.g., a Heisenberg model including spin diffusion. On the other hand, the behavior of 1/T1 vs temperature at different constant fields reveals a clear peak at temperature of the order of J/kB, qualitatively in agreement with the well-known Bloembergen–Purcell–Pound model and with previous results on semi-integer molecular spin systems. Consequently, one can suggest that for a small number N of interacting s = 1 ions (N = 8), the Haldane conjecture does not play a key role on spin dynamics, and the investigated rings still keep the quantum nature imposed mainly by the low number of magnetic centers, with no clear topological effect due to integer spins.

Measurements of proton nuclear magnetic resonance ($^{1}\mathrm{H}\phantom{\rule{0.16em}{0ex}}\mathrm{NMR}$) spectra and relaxation and of muon spin relaxation (${\ensuremath{\mu}}^{+}\mathrm{SR}$) have been performed as a function of temperature and external magnetic field on two isostructural lanthanide complexes, Er(trensal) and Dy(trensal) [where ${\mathrm{H}}_{3}\mathrm{trensal}=2,{2}^{\ensuremath{'}},{2}^{\ensuremath{'}\ensuremath{'}}\ensuremath{-}\mathrm{tris}\ensuremath{-}(\mathrm{salicylideneimino})\mathrm{triethylamine}$], featuring crystallographically imposed trigonal symmetry. Both the nuclear $1/{T}_{1}$ and muon \ensuremath{\lambda} longitudinal relaxation rates (LRRs) exhibit a peak for temperatures $T$ 30 K, associated to the slowing down of the spin dynamics, and the width of the NMR absorption spectra starts to increase significantly at $T$ \ensuremath{\sim} 50 K, a temperature sizably higher than the one of the LRR peaks. The LRR peaks have a field and temperature dependence different from those previously reported for all molecular nanomagnets. They do not follow the Bloembergen-Purcell-Pound scaling of the amplitude and position in temperature and field and thus cannot be explained in terms of a single dominating correlation time ${\ensuremath{\tau}}_{\mathrm{c}}$ determined by the spin slowing down at low temperature. Further, for $T50\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ the spectral width does not follow the temperature behavior of the magnetic susceptibility \ensuremath{\chi}. We suggest, using simple qualitative considerations, that the observed behavior is due to a combination of two different relaxation processes characterized by the correlation times ${\ensuremath{\tau}}_{\mathrm{LT}}$ and ${\ensuremath{\tau}}_{\mathrm{HT}}$, dominating for $T$ 30 K and $T50\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, respectively. Finally, the observed flattening of LRR for $T$ 5 K is suggested to have a quantum origin.

Purpose To develop a phantom for methodological radiomic investigation on Magnetic Resonance (MR) images of female patients affected by pelvic cancer. Methods A pelvis-shaped container was filled with a MnCl2 solution reproducing the relaxation times (T1, T2) of muscle surrounding pelvic malignancies. Inserts simulating multi-textured lesions were embedded in the phantom. The relaxation times of muscle and tumour were measured on an MR scanner on healthy volunteers and patients; T1 and T2 of MnCl2 solutions were evaluated with a relaxometer to find the concentrations providing a match to in vivo relaxation times. Radiomic features were extracted from the phantom inserts and the patients’ lesions. Their repeatability was assessed by multiple measurements. Results Muscle T1 and T2 were 1128 (806–1378) and 51 (40–65) ms, respectively. The phantom reproduced in vivo values within 13% (T1) and 12% (T2). T1 and T2 of tumour tissue were 1637 (1396–2121) and 94 (79–101) ms, respectively. The phantom insert best mimicking the tumour agreed within 7% (T1) and 24% (T2) with in vivo values. Out of 1034 features, 75% (95%) had interclass correlation coefficient greater than 0.9 on T1 (T2)-weighted images, reducing to 33% (25%) if the phantom was repositioned. The most repeatable features on phantom showed values in agreement with the features extracted from patients’ lesions. Conclusions We developed an MR phantom with inserts mimicking both relaxation times and texture of pelvic tumours. As exemplified with repeatability assessment, such phantom is useful to investigate features robustness and optimise the radiomic workflow on pelvic MR images.

In this work we present a detailed NMR and ${\ensuremath{\mu}}^{+}\mathrm{SR}$ investigation of the spin dynamics in the new hydrated sodium salt containing the single-ion magnet ${[\mathrm{Er}{({\mathrm{W}}_{5}{\mathrm{O}}_{18})}_{2}]}^{9\ensuremath{-}}$. The $^{1}\mathrm{H}\phantom{\rule{0.16em}{0ex}}\mathrm{NMR}$ absorption spectra at various applied magnetic fields present a line broadening on decreasing temperature which indicates a progressive spin freezing of the single-molecule magnetic moments. The onset of quasistatic local magnetic fields, due to spin freezing, is observed also in the muon relaxation curves at low temperature. Both techniques yield a local field distribution of the order of 0.1--0.2 T, which appears to be of dipolar origin. On decreasing the temperature, a gradual loss of the $^{1}\mathrm{H}\phantom{\rule{0.16em}{0ex}}\mathrm{NMR}$ signal intensity is observed, a phenomenon known as wipe-out effect. The effect is analyzed quantitatively on the basis of a simple model which relies on the enhancement of the NMR spin-spin, ${T}_{2}^{\ensuremath{-}1}$, relaxation rate due to the slowing down of the magnetic fluctuations. Measurements of spin-lattice relaxation rate ${T}_{1}^{\ensuremath{-}1}$ for $^{1}\mathrm{H}\phantom{\rule{0.16em}{0ex}}\mathrm{NMR}$ and of the muon longitudinal relaxation rate \ensuremath{\lambda} show an increase as the temperature is lowered. However, while for the NMR case the signal is lost before reaching the very slow fluctuation region, the muon spin-lattice relaxation \ensuremath{\lambda} can be followed until very low temperatures and the characteristic maximum, reached when the electronic spin fluctuation frequency becomes of the order of the muon Larmor frequency, can be observed. At high temperatures, the data can be well reproduced with a simple model based on a single correlation time $\ensuremath{\tau}={\ensuremath{\tau}}_{0}\phantom{\rule{0.16em}{0ex}}\mathrm{exp}(\mathrm{\ensuremath{\Delta}}/\mathrm{T})$ for the magnetic fluctuations. However, to fit the relaxation data for both NMR and ${\ensuremath{\mu}}^{+}\mathrm{SR}$ over the whole temperature and magnetic field range, one has to use a more detailed model that takes into account spin-phonon transitions among the $\mathrm{E}{\mathrm{r}}^{3+}$ magnetic sublevels. A good agreement for both proton NMR and ${\ensuremath{\mu}}^{+}\mathrm{SR}$ relaxation is obtained, which confirms the validity of the energy level scheme previously calculated from an effective crystal field Hamiltonian.

The kinetics of cement hydration has been studied by 1 H-NMR, through the analysis of the Free Induction Decay (FID) combined with quasi-continuous T 1 relaxation time distributions analysis, operating a sort of 2D T 1 – T 2 correlation analysis on a somewhat more physical than mathematical basis. The analysis allowed us to distinguish two solid components, SS (Solid-Short) with T 1 of a few milliseconds and SL (Solid-Long) with T 1 of the order of a second, ascribable to 1 H of anisotropically bound groups in the C–S–H gel, and to 1 H nuclei of the Portlandite crystals and possibly to crystal water in Ettringite crystals, respectively. A liquid-like component LS (Liquid-Short) with very short T 2 (∼80 μs) and T 1 a few milliseconds, both quite stable during hydration, was isolated and interpreted as water confined in the inter-layer spaces of the gel. Amounts of LS and SS increase together steadily during hydration, and these, divided by LL (Liquid-Long, the signal from the water in the pores), are proportional to 1/ T 1 for LL, confirming a surface relaxation effect for LL.

Muon spin rotation measurements were used to investigate the spin dynamics of heterometallic ${\mathrm{Cr}}_{7}\mathrm{Ni}$ and ${\mathrm{Cr}}_{7}\mathrm{Ni}$-Cu-${\mathrm{Cr}}_{7}\mathrm{Ni}$ molecular clusters. In ${\mathrm{Cr}}_{7}\mathrm{Ni}$ the magnetic ions are arranged in a quasiplanar ring and interact via an antiferromagnetic exchange coupling constant $J$, while ${\mathrm{Cr}}_{7}\mathrm{Ni}$-Cu-${\mathrm{Cr}}_{7}\mathrm{Ni}$ is composed of two ${\mathrm{Cr}}_{7}\mathrm{Ni}$ linked by a bridging moiety containing one Cu ion, that induces an inter-ring ferromagnetic interaction ${J}^{\ensuremath{'}}\ensuremath{\ll}J$. The longitudinal muon relaxation rate $\ensuremath{\lambda}$ collected at low magnetic fields ${\ensuremath{\mu}}_{0}Hl0.15$ Tesla, shows that the two systems present differences in spin dynamics vs temperature. While both samples exhibit a main peak in the muon relaxation rate vs temperature, at $T\ensuremath{\sim}10$ K for ${\mathrm{Cr}}_{7}\mathrm{Ni}$ and $T\ensuremath{\sim}8$ K for ${\mathrm{Cr}}_{7}\mathrm{Ni}$-Cu-${\mathrm{Cr}}_{7}\mathrm{Ni}$, the two compounds have distinct additional features: ${\mathrm{Cr}}_{7}\mathrm{Ni}$ shows a shoulder in $\ensuremath{\lambda}(T)$ for $Tl8$ K, while ${\mathrm{Cr}}_{7}\mathrm{Ni}$-Cu-${\mathrm{Cr}}_{7}\mathrm{Ni}$ shows a flattening of $\ensuremath{\lambda}(T)$ for $Tl2$ K down to temperatures as low as $T=20$ mK. The main peak of both systems is explained by a Bloembergen-Purcell-Pound (BPP)-like heuristic fitting model that takes into account of a distribution of electronic spin characteristic times for $Tg5$ K, while the shoulder presented by ${\mathrm{Cr}}_{7}\mathrm{Ni}$ can be reproduced by a BPP function that incorporates a single electronic characteristic time theoretically predicted to dominate for $Tl5$ K. The flattening of $\ensuremath{\lambda}(T)$ in ${\mathrm{Cr}}_{7}\mathrm{Ni}$-Cu-${\mathrm{Cr}}_{7}\mathrm{Ni}$ occurring at very low temperature can be tentatively attributed to field-dependent quantum effects and/or to an inelastic term in the spectral density of the electronic spin fluctuations.

In this work, we present a nuclear magnetic resonance (NMR) study of the spin dynamics in the rare-earth-based low-dimensional molecular magnetic chains $\mathrm{Eu}{(\mathrm{hfac})}_{3}\mathrm{NITEt}$ and $\mathrm{Gd}{(\mathrm{hfac})}_{3}\mathrm{NITEt}$ (in short, Eu-Et and Gd-Et). Although both samples are based on the same chemical building block, [(${\mathrm{hfac})}_{3}\mathrm{NITEt}]$, their magnetic properties change dramatically when the ${\mathrm{Eu}}^{3+}$ ion, which is nonmagnetic at low temperatures, is substituted by the magnetic ${\mathrm{Gd}}^{3+}$ ion. The present proton NMR investigation shows that, down to the lowest investigated temperature ($T=1.5$ K for Gd-Et and $T=3$ K for Eu-Et), the Eu-Et chain behaves as a one-dimensional Heisenberg model with antiferromagnetic exchange coupling ($J=\ensuremath{-}20$ K) between $s=1/2$ organic radicals, and has a $T$-independent exchange frequency (${\ensuremath{\omega}}_{e}=2.6\ifmmode\times\else\texttimes\fi{}{10}^{12}$ rad/s). In the Gd-Et chain, in contrast, a competition arises between nearest-neighbor ferromagnetic coupling and next-nearest-neighbor antiferromagnetic coupling; moreover, two phase transitions have previously been found, in agreement with Villain's conjecture: a first transition, at ${T}_{0}=2.2$ K, from a high temperature paramagnetic phase to a chiral spin liquid phase, and a second transition, at ${T}_{N}=1.9$ K, to a three-dimensional helical spin solid phase. Contrary to the Eu-Et chain (whose three-dimensional ordering temperature is estimated to insurge at very low, ${T}_{N}\ensuremath{\approx}0.3$ K), critical spin dynamics effects have been measured in the Gd-Et chain on approaching ${T}_{N}=1.9$ K: namely, a divergence of the proton nuclear spin-lattice relaxation rate $1/{T}_{1}$, which in turn produces a sudden wipe-out of the NMR signal in a very narrow ($\mathrm{\ensuremath{\Delta}}T\ensuremath{\sim}0.04$ K) temperature range above ${T}_{N}$. Below ${T}_{N}$, an inhomogeneous broadening of the NMR line indicates a complete spin freezing. At ${T}_{0}=2.2$ K, instead, such critical effects are not observed because NMR measurements probe the two-spin correlation function, while the chiral spin liquid phase transition is associated with a divergence of the four-spin correlation function.

We present NMR and μ+SR study of spin dynamics in one-dimensional and quasi-one-dimensional molecular magnets of recent synthesis. In particular, we focus on the so called Gd(hfac)3NIT-R and CoPhOMe magnetic chains families. For Gd-R helimagnets we show some differences between “weakly frustrated systems” and “fully frustrated systems”. The different behaviour is due to the different radical inserted in the chains (R = Me, Ph for “weakly frustrated systems” and R = iPr, Et for “fully frustrated systems”). The existence of different phase transitions, particularly to 3D long-range magnetic order in Gd-Ph and to chiral order in Gd-iPr, is remarked together with a comparison between results obtained from macroscopic and microscopic investigating techniques. As regards CoPhOMe slowly relaxing chain, the 1H NMR measurements confirm the freezing of the spins at low temperature, which prevents the 3D long-range order, and display the presence of two relaxation mechanisms related to distinct contributions to the local spin relaxation.

Mediterranean corals are a natural model for studying global warming, as the Mediterranean basin is expected to be one of the most affected regions and the increase in temperature is one of the greatest threats for coral survival. We have analyzed for the first time with time-domain nuclear magnetic resonance (TD-NMR) the porosity and pore-space structure, important aspects of coral skeletons, of two scleractinian corals, Balanophyllia europaea (zooxanthel- late) and Leptopsammia pruvoti (nonzooxanthellate), taken from three different sites on the western Italian coast along a temperature gradient. Comparisons have been made with mercury intrusion porosimetry and scanning electron micros- copy images. TD-NMR parameters are sensitive to changes in the pore structure of the two coral species. A parameter, related to the porosity, is larger for L. pruvoti than for B. europaea, confirming previous non-NMR results. Another parameter representing the fraction of the pore volume with pore sizes of less than 10−20 μm is inversely related, with a high degree of statistical significance, to the mass of the specimen and, for B. europaea, to the temperature of the growing site. This effect in the zooxanthellate species, which could reduce its resistance to mechanical stresses, may depend on an inhibition of the photosynthetic process at elevated temperatures and could have particular consequences in determining the effects of global warming on these species.

We report a broadband H-1 NMR study of the spin dynamics of coated maghemite and goldmaghemite hybrid nanostructures with two different geometries, namely dimers and coreshells. All the samples have a superparamagnetic behavior, displaying a blocking temperature (T-B similar to 80 K (maghemite), similar to 105 K (dimer), similar to 150 K (coreshell)), and the magnetization reversal time follows the VogelFulcher law. We observed three different anomalies in H-1 NMR T(1)1 versus T that decrease in amplitude when increasing the applied magnetic field. We suggest that the anomalies are related to three distinct system dynamics: molecular rotations of the organic groups (240 < T < 270 K), superparamagnetic spin blockage (100 < T < 150 K), and surfacecore spin dynamics (T < 25 K). By fitting the T(1)1 data with a heuristic model, we achieved a good agreement with magnetic relaxation data and literature values for methyl group rotation frequencies.

Ocean acidification is predicted to impact ecosystems reliant on calcifying organisms, potentially reducing the socioeconomic benefits these habitats provide. Here we investigate the acclimation potential of stony corals living along a pH gradient caused by a Mediterranean CO2 vent that serves as a natural long-term experimental setting. We show that in response to reduced skeletal mineralization at lower pH, corals increase their skeletal macroporosity (features >10 μm) in order to maintain constant linear extension rate, an important criterion for reproductive output. At the nanoscale, the coral skeleton's structural features are not altered. However, higher skeletal porosity, and reduced bulk density and stiffness may contribute to reduce population density and increase damage susceptibility under low pH conditions. Based on these observations, the almost universally employed measure of coral biomineralization, the rate of linear extension, might not be a reliable metric for assessing coral health and resilience in a warming and acidifying ocean., Global warming and ocean acidification impact coral ecosystems. Here, the authors show higher skeletal porosity and reduced bulk density at lower pH in corals living along a natural pH gradient in the Mediterranean, which may contribute to reduce population density and increase damage susceptibility.

The quasi-continuous distributions of spin-lattice (T 1) and spin-spin (T 2) relaxation times of a population of cells kept under stress conditions for about 400 h has been obtained by 1H-NMR relaxometry. The comparison with the results obtained from the analysis of cell viability and morphological variations by phase contrast optical microscopy and performed with acquisition times, duration and conditions matching those of the relaxometry experiments allowed us to identify three main phases of the processes related to the exchanges of water and remodeling of cellular compartments: between 0 and 40 h the intra- and extra-cellular compartments are characterized by a T 2 of ~250 ms and of ~2 s respectively and the cell population half-life has been experimentally evaluated to be ~45 h; after 40 and until 100 h cells NMR parameter changes suggest that the confined water is increasing according to the progressive fragmentation of the cells membrane; over 100 h almost all cells are non-viable and the constancy of the main NMR parameters reflects the reaching of the final equilibrium of the system. In conclusion our observations validated the use of NMR as a non-destructive, non-invasive powerful technique for monitoring the progression of cellular processes involving compartments water exchange and reorganization.

The spin dynamics of the molecular magnetic chain [Dy(hfac)(3){NIT(C6H4OPh)}] were investigated by means of the Muon Spin Relaxation (mu+SR) technique. This system consists of a magnetic lattice of alternating Dy(III) ions and radical spins, and exhibits single-chain-magnet behavior. The magnetic properties of [Dy(hfac)(3){NIT(C6H4OPh)}] have been studied by measuring the magnetization vs. temperature at different applied magnetic fields (H - 5, 3500, and 16500 Oe) and by performing mu+SR experiments vs. temperature in zero field and in a longitudinal applied magnetic field H - 3500 Oe. The muon asymmetry P(t) was fitted by the sum of three components, two stretched-exponential decays with fast and intermediate relaxation times, and a third slow exponential decay. The temperature dependence of the spin dynamics has been determined by analyzing the muon longitudinal relaxation rate lambda(interm)(T), associated with the intermediate relaxing component. The experimental lambda(interm)(T) data were fitted with a corrected phenomenological Bloembergen-Purcell-Pound law by using a distribution of thermally activated correlation times, which average to tau - tau(0) exp(Delta/k(B)T), corresponding to a distribution of energy barriers Delta. The correlation times can be associated with the spin freezing that occurs when the system condenses in the ground state. (C) 2015 AIP Publishing LLC.

Cement hydration occurs when water is added to cement powder, leading to the formation of crystalline products like Portlandite and the quasi-amorphous, poorly crystalline, calcium silicate hydrate (C-S-H) gel. Despite its importance in determining the final properties of the cement, many models exist for the nano and sub-nano level organization of this liquid stone. H-1 NMR relaxometry in White Portland Cement paste during hydration allowed us to monitor the formation and evolution of the multiscale porosity of the cement, with the formation of structures at nano and sub-nano levels of C-S-H gel (calcium silicate interlayer water, water in small and large gel pores) along with three low-mobility H-1 pools, identified as H-1 nuclei in C-S-H layers, likely belonging to OH groups, with H-1 nuclei in Portlandite, and in crystal water of Ettringite. By assuming these assignments, our data allowed us to compute the distances of pairs of H-1 nuclei in Portlandite and in crystal water ((1.9 +/- 0.2) angstrom and (1.6 +/- 0.1)angstrom, respectively), consistent with the known values of these distances. The picture of the porous structure at nano and sub-nano levels emerging from our results is consistent with the Jennings colloidal model for C-S-H gel. Moreover, the constant values observed during hydration of parameters extracted from our data analysis strongly support that model, being compatible with the picture of C-S-H gel developing in comparable-sized clumps of the same composition, but not easily interpretable by models proposing quasi continuous sheets of C-S-H layers.

Low-temperature magnetic susceptibility, zero-field muon spin resonance and specific heat measurements have been performed in the quasi-one-dimensional (1D) molecular helimagnetic compound Gd ( hfac ) 3 NITEt . The specific heat presents two anomalies at T 0 = 2.19 ( 2 ) K and T N = 1.88 ( 2 ) K , while susceptibility and zero-field muon spin resonance show anomalies only at T N = 1.88 ( 2 ) K . The results suggest an experimental validation of Villain's conjecture of a two-step magnetic ordering in quasi-1D XY helimagnets: the paramagnetic phase and the helical spin solid phases are separated by a chiral spin liquid, where translational invariance is broken without violation of rotational invariance.

In order to well distinguish different tissues of the human body by magnetic resonance imaging (MRI), it is of great importance to find procedures to improve the image contrast. In particular, a valuable feature is to image only specific parts of organs and/or tissues while ignoring all the others. Dedicated MRI sequences able to filter the 1 H nuclei signals based on the different longitudinal relaxation times (T1) of the tissues have been developed. Standard signal selection/attenuation sequences, such as the Short Time Inversion Recovery and Multiple Inversion Recovery, have the effect to zero the signal for a discrete number of T1 values. Parametrically Enabled Relaxation Filters with Double and multiple Inversion (PERFIDI) sequences act on a range of T1 values and behave as an electronic band-pass or high-pass or low-pass filters. PERFIDI filters are therefore primarily focused on the components that pass through, rather than on those that are blocked. These filters have been developed and tested by nuclear magnetic resonance relaxometry. Here, these sequences have been validated for MRI on phantom samples to mimic T1 distributions present in tissues. Preliminary applications show that PERFIDI filters can effectively work on a range of T1 values to give well contrasted images.

Controlled polystyrenes with different molar mass values were synthesized starting from benzoyl peroxide and TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxy). The polystyrene homopolymers served as initiators for the block copolymerization of phthalimide methylstyrene (PIMS) to synthesize polystyrene-b-poly(PIMS) diblock copolymers. Diblock copolymers with well defined structures as well as controlled and narrow molar mass distribution were obtained from the lower-mass polystyrene homopolymers. The lower-mass copolymers were found to be active as initiators in the synthesis of the polystyrene-b-poly(PIMS)-b-polystyrene triblock copolymers. In each reaction step, the effects of conversion and reaction time on the molar mass characteristics of the prepared block copolymers were investigated. The diblock and triblock copolymers were modified using hydrazine as the reagent in order to obtain the corresponding functional amino block copolymers.

Proton Nuclear Magnetic Resonance (NMR) relaxation measurements have been performed down to very low temperature (50 mK) to determine the effect of coupling two Cr7Ni molecular rings via a Cu2+ ion. No difference in the spin dynamics was found from nuclear spin lattice relaxation down to 1.5 K. At lower temperature, the H-1-NMR line broadens dramatically indicating spin freezing. From the plot of the line width vs. magnetization, it is found that the freezing temperature is higher (260 mK) in the coupled ring with respect to the single Cr7Ni ring (140 mK). (C) 2014 AIP Publishing LLC.

We present the first comparative investigation of the Nuclear Magnetic Resonance (NMR) relaxivity of a series of nanosized cyano-bridged coordination networks stabilized in aqueous solution. These Ln(3+)/[Fe(CN)(6)](3-) (Ln = Gd, Tb, Y) and M2+/[Fe(CN)(6)](3-) (M = Ni, Cu, Fe) nanoparticles with sizes ranging from 1.4 to 5.5 nm are stabilized by polyethylene glycols (MW = 400 or 1000), polyethylene glycol fiinctionalized with amine groups (MW = 1500), or by N-acetyl-D-glucosamine. The evaluation of NMR relaxivity allowed estimation of the Magnetic Resonance Imaging (MRI) contrast efficiency of our systems. The results demonstrate that Gd3+/[Fe(CN)(6)](3-) nanoparticles have r(1p) and r(2p) relaxivities about four times higher than the values observed in the same conditions for the commercial Contrast Agents (CAs) ProHance or Omniscan, regardless of the stabilizing agent used, while nanoparticles of Prussian blue and its analogues M2+/[Fe(CN)(6)](3-) (M = Ni, Cu, Fe) present relatively modest values. The influence of the chemical composition of the nanoparticles, their crystal structure, spin values of lanthanide and transition metal ions, and stabilizing agent on the relaxivity values are investigated and discussed.

We investigate the phonon-induced relaxation dynamics in the Fe-7 magnetic molecule, which is made of two Fe3+ triangles bridged together by a central Fe3+ ion. The competition between different antiferromagnetic exchange interactions leads to a low-spin ground state multiplet with a complex pattern of low-lying excited levels. We theoretically investigate the decay of the time correlation function of molecular observables, such as the cluster magnetization, due to the spin-phonon interaction. We find that more than one time contributes to the decay of the molecular magnetization. The relaxation dynamics is probed by measurements of the nuclear spin-lattice relaxation rate 1/T-1. The interpretation of these measurements allows the determination of the magnetoelastic coupling strength and to set the scale factor of the relaxation dynamics time scales. In our theoretical interpretation of 1/T-1 data we also take into account the wipeout effect at low temperatures.

We present the magnetic properties of three recently synthesized binuclear molecular complexes [NiNd], [NiGd], and [ZnGd] investigated by dc magnetization and proton nuclear magnetic resonance (NMR) measurements. The high-temperature magnetic properties are related to the independent paramagnetic behavior of the two magnetic metal ions within the binuclear entities both in [NiNd] and [NiGd]. On lowering the temperature, the formation of a magnetic dimer, with a low-spin ground state due to antiferromagnetic interaction ($J$/${k}_{B}$ \ensuremath{\approx} \ensuremath{-}25 K) between Ni${}^{2+}$ and Nd${}^{3+}$, is found in the case of [NiNd], while in [NiGd], a ferromagnetic interaction ($J$/${k}_{B}$ \ensuremath{\approx} 3.31 K) between the magnetic ions leads to a high-spin ($S$ $=$ 9/2) ground state. The temperature dependence of the proton nuclear spin lattice relaxation rate ${T}_{1}$${}^{\ensuremath{-}1}$ in [NiNd] is driven by the fluctuation of the hyperfine field at the nuclear site due to relaxation of the magnetization. At high temperatures, the independent Ni${}^{2+}$ and Nd${}^{3+}$ spins fluctuate fast, while at low temperatures, we observe a slowing down of the fluctuation in the total magnetization of the dimer because of the insurgence of antiferromagnetic spin correlations. The relaxation mechanism in [NiNd] at low temperatures is interpreted by a single temperature-dependent correlation frequency ${\ensuremath{\omega}}_{\mathrm{c}}$ \ensuremath{\propto} ${T}^{3.5}$, which reflects the lifetime broadening of the exchange-coupled spins via spin-phonon interaction. The proton NMR signal in [NiGd] could just be detected at room temperature due to the shortening of relaxation times when $T$ is decreased. The magnetic properties of [ZnGd] are the ones expected from a weakly interacting assembly of isolated moments except for anomalies in the susceptibility and NMR results below 15 K, which currently cannot be explained.

The static and dynamic properties of the single-chain molecular magnet [Co(hfac)$_2$NITPhOMe] are investigated in the framework of the Ising model with Glauber dynamics, in order to take into account both the effect of an applied magnetic field and a finite size of the chains. For static fields of moderate intensity and short chain lengths, the approximation of a mono-exponential decay of the magnetization fluctuations is found to be valid at low temperatures; for strong fields and long chains, a multi-exponential decay should rather be assumed. The effect of an oscillating magnetic field, with intensity much smaller than that of the static one, is included in the theory in order to obtain the dynamic susceptibility $\chi(\omega)$. We find that, for an open chain with $N$ spins, $\chi(\omega)$ can be written as a weighted sum of $N$ frequency contributions, with a sum rule relating the frequency weights to the static susceptibility of the chain. Very good agreement is found between the theoretical dynamic susceptibility and the ac susceptibility measured in moderate static fields ($H_{\rm dc}\le 2$ kOe), where the approximation of a single dominating frequency turns out to be valid. For static fields in this range, new data for the relaxation time, $\tau$ versus $H_{\rm dc}$, of the magnetization of CoPhOMe at low temperature are also well reproduced by theory, provided that finite-size effects are included., Comment: 16 pages, 9 figures

We present magnetic susceptibility, $^{1}\text{H}$ nuclear magnetic resonance (NMR) spectra, spin-spin- and spin-lattice-relaxation rates data, collected in the temperature range $1.65lTl300\text{ }\text{K}$ at two applied magnetic fields $H=0.35$ and 1.5 T, on a single crystal of ${\text{Cr}}_{7}\text{Fe}$ heterometallic molecular nanomagnet. From a simple analysis of the magnetic susceptibility data, we deduce that the ring has a magnetic total spin ${S}_{T}=1/2$ ground state and Cr-Cr antiferromagnetic (AFM) exchange interactions comparable to similar ${\text{Cr}}_{7}\text{M}$ heterometallic rings. The proton NMR data indicate that the main coupling between nuclei and electronic moments is of dipolar origin. The spin-lattice-relaxation rate behavior is qualitatively explained by a model which assumes a single-correlation time as used previously for homometallic AFM rings. The direct comparison of the relaxation data in ${\text{Cr}}_{7}\text{Fe}$ and ${\text{Cr}}_{8}$ shows a substantial change in the spin dynamics as the result of Fe replacing one Cr ion. The difference is attributed to the change in the elastic properties of the sample with Fe substitution and/or to the multi-Lorentzian behavior of the spin-spin correlation function resulting from the presence of inequivalent ions in the heterometallic ring.

The magnetic properties and the spin dynamics of two molecular magnets have been investigated by magnetization and dc susceptibility measurements, electron paramagnetic resonance and proton nuclear magnetic resonance (NMR) over a wide range of temperatures (1.6\char21{}300K) at applied magnetic fields $H=0.5$ and 1.5 T. The two molecular magnets consist of $\phantom{[}{\phantom{{}{\text{Cu}}^{\text{II}}(\text{saldmen})({\text{H}}_{2}\text{O})}}_{6}{{\text{Fe}}^{\text{III}}{(\text{CN})}_{6}}]{({\text{ClO}}_{4})}_{3}\ensuremath{\cdot}8{\text{H}}_{2}\text{O}$ in short ${\text{Cu}}_{6}\text{Fe}$ (here H saldmen is the Schiff base resulted by reacting salicylaldehyde with N,N-dimethylethylenediamine) and the analog compound with cobalt, ${\text{Cu}}_{6}\text{Co}$. It is found that in ${\text{Cu}}_{6}\text{Fe}$, whose magnetic core is constituted by six ${\text{Cu}}^{2+}$ ions and one ${\text{Fe}}^{3+}$ ion all with $s=1/2$, a weak ferromagnetic interaction between ${\text{Cu}}^{2+}$ moments through the central ${\text{Fe}}^{3+}$ ion with $J=0.14\text{ }\text{K}$ is present, while in ${\text{Cu}}_{6}\text{Co}$ the ${\text{Co}}^{3+}$ ion is diamagnetic and the weak interaction is antiferromagnetic with $J=\ensuremath{-}1.12\text{ }\text{K}$. The NMR spectra show the presence of nonequivalent groups of protons with a measurable contact hyperfine interaction consistent with a small admixture of $s$ wave function with the $d$ function of the magnetic ion. The NMR relaxation results are explained in terms of a single-ion $({\text{Cu}}^{2+},\text{ }{\text{Fe}}^{3+},\text{ }{\text{Co}}^{3+})$ uncorrelated spin dynamics with an almost temperature-independent correlation time due to the weak magnetic exchange interaction. We conclude that the two molecular magnets studied here behave as single-molecule paramagnets with a very weak intramolecular interaction, almost on the order of the dipolar intermolecular interaction. Thus they represent a separate class of molecular magnets which differ from the single-molecule magnets investigated up to now, where the intramolecular interaction is much larger than the intermolecular one.

Crystals containing Ni 10 magnetic molecules display an unprecedented form of out-of-equilibrium behavior of the bulk magnetization M at temperatures as high as 17 K. We have performed 1 H NMR measurements to probe the local Ni magnetic moments and their dynamics. It is apparent that no freezing of the Ni moments occurs, in striking contrast to what is observed in blocked superparamagnetic systems. The average local moments display the same behavior as M, thus unambiguously demonstrating the intrinsic character of the phenomenon. This result supports the hypothesis that the slowing down of M is due to a resonant phonon trapping mechanism which prevents the thermalization of M but not the fast spin flippings of the individual molecular moments. Indeed, the measured nuclear spin-lattice relaxation rate points to fast single-molecule dynamics at low temperature.

We investigated the spin dynamics of Zn(II)-doped “single-chain magnet” (SCM) Co(hfac)2NITPhOMe (in short CoPhOMe) by means of 1H NMR measurements. CoPhOMe was the first magnetic chain that showed a slowly relaxing magnetization (commonly called spins’ or magnetization “slowing down” mechanism), which follows the predictions of the Glauber model: the electronic spin freezing sets in before any transition to long-range magnetic order. The slowing down of the magnetization is also evidenced in the Zn-doped samples, which present chains that reach an average length of some tenth of spins for the highest doping, together with growing finite-size effects as the doping concentration is increased. The nuclear spin–lattice relaxation rate T1-1(T) at different applied magnetic fields, displayed a high-temperature peak and a low-temperature shoulder that become lower and shifts toward higher temperatures with increasing the field. This behaviour is qualitatively in agreement with the recent AC susceptibility data that revealed the Glauber dynamics and finite-size effects, like the collective reversal of the spins of each chain segment.

Low-temperature specific heat, magnetic susceptibility, and zero-field muon spin resonance (MUSR) measurements have been performed in the quasi-one-dimensional molecular helimagnetic compound Gd(hfac)(3)NITEt. The specific heat presents two anomalies at T(0)=2.19 +/- 0.02 K and T(N)=1.88 +/- 0.02 K, which both disappear upon the application of a weak magnetic field. Conversely, magnetic susceptibility and mu SR data show the divergence of two-spin correlation functions only at T(N)=1.88 +/- 0.02 K. These results suggest an experimental validation of Villain's conjecture of a two-step magnetic ordering in quasi-one-dimensional XY helimagnets; i.e., the paramagnetic phase and the helical spin solid phase are separated by a chiral spin liquid phase, where translational invariance is broken without violation of rotational invariance.

We present magnetization and (1)H nuclear magnetic resonance (NMR) measurements performed in both closed Cr8 and open Cr8Zn antiferromagnetic molecular rings in the temperature range 1.65

International audience; Magnetic resonance imaging (MRI) is at the forefront of non-invasive medical imaging techniques. It provides good spatial and temporal resolution that can be further improved by the use of contrast agents (CAs), providing a valuable tool for diagnostic purposes. Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are attractive MRI contrast agents due to their negative (T-2) contrast enhancement capability and biocompatibility. Clusters of USPIOs with polymer material are of particular interest since they can sustain additional functionalities like drug delivery and targeting. Aiming to establish a relationship between the morphology of the clusters and their efficacy as MRI contrast agents (relaxometric properties), we prepared - using three different maghemite (gamma-Fe2O3) USPIO diameters - a series of hybrid copolymer/iron oxide CAs presenting two different geometries (micellar or vesicular). The NMR relaxometry profiles confirmed the nature of the physical mechanisms inducing the increase of nuclear relaxation rates at low (magnetic anisotropy) and high (Curie relaxation) magnetic fields. A heuristic model, first proposed by Roch, Muller, Gillis, and Brooks, allowed the fitting of the whole longitudinal relaxivity r(1)(v) profile, for samples with different magnetic core sizes. We show that both types of clusters exhibit transverse relaxivity (r(2)) values comparable to or higher than those of common contrast agents, over the whole tested frequency range. Moreover, in-depth analysis revealed substantially a linear relationship between r(2) and the number of encapsulated USPIOs divided by the diameter of the clusters (N-USPIO/D-H), for each USPIO size. The cluster structure (i.e. micelle or vesicle) appeared to have a mild influence on the transverse relaxivity value. Indeed, the r(2) value was mainly governed by the individual size of the USPIOs, correlated with both the cluster external diameter and the magnetic material volume fraction.

Nuclear magnetic resonace $(\mathrm{NMR})$, $\mathrm{EPR}$ and magnetization measurements in ${\mathrm{Na}}_{x}{\mathrm{CoO}}_{2}$ for $0.65\ensuremath{\leqslant}x\ensuremath{\leqslant}0.75$ are presented. While the $\mathrm{EPR}$ signal arises from ${\mathrm{Co}}^{4+}$ magnetic moments ordering at ${T}_{\mathrm{c}}\ensuremath{\simeq}26\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, $^{59}\mathrm{Co}$ $\mathrm{NMR}$ signal originates from cobalt nuclei in metallic regions with no long range magnetic order and characterized by a generalized susceptibility typical of strongly correlated metallic systems. This phase separation in metallic and magnetic insulating regions is argued to occur below ${T}^{*}(x)$ $(220--270\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. Above ${T}^{*}$ an anomalous decrease in the intensity of the $\mathrm{EPR}$ signal is observed and associated with the delocalization of the electrons which for $Tl{T}^{*}$ were localized on ${\mathrm{Co}}^{4+}\phantom{\rule{0.3em}{0ex}}{d}_{{z}^{2}}$ orbitals. It is pointed out that the in-plane antiferromagnetic coupling $J⪡{T}^{*}$ cannot be the driving force for the phase separation.

"We present the magnetic properties and the H-1 nuclear magnetic resonance dispersion profiles of Mn-ferrites-based compounds, as possible novel contrast agents (CAs) for magnetic resonance imaging (MRI). The samples consist of nanoparticles (NPs) with the magnetic core made of Mn1+xFe2-xO4, obtained by the rapid decomposition of metalcarbonyl into a hot solvent containing an oxidizer and a coordinating surfactant; by this procedure, monodisperse capped NPs with different sizes have been obtained. We have performed structural and morphological investigation by x-ray powder diffraction and transmission electron microscopy techniques and SQUID magnetometry experiments to investigate the magnetic behaviour of the samples. As required for MRI applications using negative CAs, the samples are superparamagnetic at room temperature, having blocking temperatures in the range 14-80 K. The longitudinal r(1) and transverse r(2) nuclear relaxivities appear to vary strongly with the magnetic core size, their values being comparable to commercial compounds in the high-frequency range nu > 100 MHz. The experimental results suggest that our samples are suitable for high-frequency MRI imagers in general and in particular for the 3 T clinical imager, as indeed suggested by a recent report (Tromsdorf et al 2007 Nanoletters 7 2422)."

We present specific heat, susceptibility and MUSR study of quasi-one-dimensional Gd(hfac)3NITR helimagnets of recent synthesis. In particular we focus our attention on Gd(hfac)3NITiPr fully frustrated system which shows two different kinds of phase transitions: the first one related to chiral order and the second one to 3D long-range helical order.